Processing equipment of this nature is widely used for a variety of operations including the control of machine tools in industrial plants or the establishment and termination of connections in telecommunication exchanges, for example. In all these instances it is important to detect and localize any possible malfunctions in real time so that a defective component can be quickly replaced by a spare. As a rule, the units used for checking on the proper performance of the operating equipment must work with a higher degree of reliability than the equipment itself in order to prevent, on the one hand, the emission of erroneous alarm indications and, on the other hand, the nonrecognition of defects. At the same time, these checking units must not unduly encumber the processing system and must not interfere with the normal operation of the equipment supervised thereby.
Conventional self-checking system for processing equipment of the type here envisaged are relatively complex and occupy large portions of the program memories associated with such equipment. These systems are therefore not well suited for the supervision of smaller components such as microprocessors utilizing memories of limited capacity.